Aircraft landing lights are primarily intended to illuminate the runway directly ahead of the aircraft, with a secondary function of making the aircraft visible to other aircraft. For smaller airplanes, there may be a single landing light mounted near a lower portion of the front of the airplane. For larger aircraft, there may be multiple landing lights mounted on or near the underside of the airplane, typically near the front landing gear and the underside of the wings near the fuselage, although other locations may also be used. In general, landing lights should be extremely bright in an area or angular range directly in front of the aircraft (sometimes referred to as the “hot spot”), as well as require as little electrical power as possible, be lightweight and durable, and have relatively long lifetimes.
Historically, most landing lights have used incandescent light sources in the “PAR” bulb configuration, which includes a parabolic aluminized reflector. Light leaving the filament toward the transparent portion of the bulb leaves the bulb, and light that misses the transparent portion of the bulb generally reflects off the parabolic reflector and exits the bulb in a generally collimated beam that is superimposed with the directly-exiting light from the filament. In general, these bulbs tend to produce a single bright “hot spot” directly in front of the airplane, with very little illumination elsewhere.
There have been numerous attempts to use LEDs as the light source for various applications. For instance, LED-based vehicle lights or light systems are disclosed in U.S. Pat. No. 7,686,486 (Tessnow), U.S. Pat. Appln. Pub. 2005/0073849 (Rhoads), U.S. Pat. No. 7,806,562 (Behr), U.S. Pat. Appln. Pub. 2009/0213606 (Coushaine), U.S. Pat. No. 7,896,532 (Hsu), U.S. Pat. No. 7,134,774 (Iwasaki). Example LED spotlights are disclosed in U.S. Pat. No. 6,814,470 (Rizkin) and U.S. Pat. No. 7,758,204 (Klipstein). Example components for LED-based lights include a toroidal lens disclosed in U.S. Pat. Appln. Pub. 2008/0310166 (Chinniah), a light-source multiplication device disclosed in U.S. Pat. No. 4,965,488 (Hihi), and a reflective element formed from portions of multiple ellipsoids disclosed in U.S. Pat. No. 7,753,574 (Meyrenaud). An example module that features a linear array of five LEDs with controlling circuitry, emitting from the center of a 50 mm diameter cylindrical housing, is currently sold under the name “JOULE® JFL2 LED System” by Osram Sylvania Inc. of Danvers, Mass.
There is an ongoing need for further improved LED systems. When compared with conventional incandescent bulb-based systems, the LED systems may be smaller, may have significantly longer lifetimes, may require significantly less electrical power for operation, and may provide additional illumination in visible regions other than the “hot spot” directly in front of the airplane.